In the description below, the expression “fluid line” should be understood to mean any tubular structure comprising a peripheral wall laterally delimiting a space in which a fluid can circulate, and comprising an inlet and an outlet. The transversal section of a fluid line can be of any form (circular, polygonal, etc.), constant or not along the line. A capillary tube, a duct, a pipeline are all synonyms of the concept of fluid line as used in the invention.
The functionalization of a surface is the operation by which one or more molecule(s) of interest are fastened onto a surface, so that it/they retains/retain all or part of its/their properties. The functionalization of a surface therefore presupposes that both the molecule of interest and an associated method for fastening it onto the surface are available.
Several types of surface functionalization methods are known from the prior art. Traditionally, they consist in modifying the surface to be functionalized through chemical reactions aiming to generate functions which can be reactivated with regard to a probe molecule. Said probe molecule then being used to pick up a target whose presence is ultimately to be detected.
The main difficulties encountered in these surface functionalizations lie in the choice of reactive chemical functions that can be implemented to obtain the immobilization of the probe on the surface of a support. For example, the chemical nature of the surface of the support has to be taken into account.
In the case of a silicon substrate, the molecules of silane type are widely used. A molecule is then employed which exhibits a silane function which can react with the support made of silicon via the surface silanols and a reactive function that may or may not be masked with respect to a probe molecule, possibly chemically modified. Once the silane is fixed on the surface of the support, the probe molecule is positioned on the silane molecule by the use of complementary reactive functions.
To delimit on a support, made of silicon for example, the areas which will have to undergo a functionalization, use is conventionally made of the techniques of localized reactions by automaton (or “spotting”) that make it possible to accurately locate the ejection of the silane and, consequently, to define successive and isolated areas that are functionalized by silanes of different natures.
Nevertheless, this technique cannot be considered in the case where the surface of the support is made inaccessible to the spotting. In particular, in the case where the aim is to discretize the areas of a surface situated on the internal face of a sealed cavity.
Using this assumption, provision can be made, for example, to locally modify the wettability of the surface of the support prior to its placement in a more complex device in order to subsequently preferentially guide the reagents including the silanes to the modified areas of wettability. Also, it is possible to modify the surface of the support via the introduction of metallic contacts which are electrically connected and can be used for electrografting.
However, the abovementioned techniques require significant modifications to the structure of the surface, adding to the complexity of the production of micromechanical devices that are already sufficiently complex.
There are also silanes that have a function masked by a photolabile grouping. After fixing onto the surface of a support, said silanes are deprotected to release a function which is itself reactive with respect to a complementary function borne by a probe molecule. By the use of a selective insolation, the photodeprotection can be localized and make it possible to differentiate areas on the surface of the support.
From the use of this type of silane, the need to render the surface accessible to the insolation conditions will be understood, which consequently poses a problem when the surface to be functionalized selectively forms part of a closed cavity whose walls are opaque, for example made of silicon or of another opaque material.
Most of the methods of functionalization through photochemical means that are known are applied to the functionalization of a planar surface, directly lit for the photochemical reaction. Since the lighting of the surface is direct, the nature of the support is involved only in the chemical reaction itself, and not in the possibility of activating it by lighting. The supports used can therefore be made of plastic, of glass, of silicon, or any other opaque material.